B body front drum brakes on A body?

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JoeDust451

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What all is involved, seems like a fairly simple swap, what years should i look for? I'm wanting to convert to the LBP, this seems like the easiest & cheapest way.
 
this prolly wont help, BUT...i think it would be more beneficial for you to swap for disc brakes, rather than to find a set of b body drums, rebuild them, and use all ur time to install them...only to have...drum brakes...i think you will be much happier with disc brakes, my friend!
 
mopardude318 said:
this prolly wont help, BUT...i think it would be more beneficial for you to swap for disc brakes, rather than to find a set of b body drums, rebuild them, and use all ur time to install them...only to have...drum brakes...i think you will be much happier with disc brakes, my friend!
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I figured i would get this kind of responce, its just that finding an F body around my area that still has all its disc brakes is non existant for the most part, & i don't feel like changing MCers & P valve & re-fabeing brake lines, plus the exspence of buying all the stuff needed to convert it over, drum brakes seem like the cheapest & simpleist sollution.
 
F, M, J and late B all have the disc brakes you can use. There must be some over there in TX for you to strip the pieces off. Really I dont think you would save much at all by going with B drum brakes and you wont improve your braking appreciably.
Which of your A's are you wanting to do this to?
 
I'm in Mo. now, its on a 71 Swinger i'm building, so what years of the FMJ & later B bodies do i need to look for?
 
hey joe,
i do agree with going to disc. brakes, but if so i do have the complete drum brake set up on a 68 ply belvedere. let me know...thk.junebug
 
JoeDust451 said:
What all is involved, seems like a fairly simple swap, what years should i look for? I'm wanting to convert to the LBP, this seems like the easiest & cheapest way.
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The next A-body configuration is the disc-brakes. These were available 1965-1970 as the same interchange.

Actually mid '65 through '72 used the same small-bolt 4-piston Kelsey-hayes disc brakes, with the *only* difference being that the '71-'72 cars used RH threads on the lugs on both sides of the car.
The 1971 and 1972 cars are the same part with the 1973 and up the 4 1/2", bolt pattern.
This is a completely different, single-piston setup which also is used on the F-bodies (Aspen, Volare). There are quite a number of swaps and parts optimizations possible within the '73 and up disc brakes.
It is possible to swap any of the A-bodies to disc brakes by using everything between the upper and lower control arms. When going from a drum to disc front brake setup, it is easier to buy the Mopar performance proportioning valve, than to change the master cylinder.
This is partly correct. Disc brake master cylinders differ from drum brake items in several respects. One such respect is that it is ESSENTIAL that a master cylinder (or section of a master cylinder) used with disc brakes NOT HAVE A PRESSURE RESIDUAL VALVE!! This is a small rubber flapper valve located behind the tube seat. Its function is to keep small ("residual") pressure on a drum brake system to avoid air being sucked in at the wheel cylinders. This does not create a problem with brake dragging, because drum brakes use strong springs to pull the shoes back. Discs rely on a complete lack of system pressure and the deformation of the piston seal to pull the piston and the shoe back ever so slightly from the disc. Residual pressure in a disc system will prevent this release and cause brake wear and heat buildup. Also, disc brake master cylinders have much larger reservoirs to cope with the fact that disc brakes have a much higher fluid carrying volume. This isn't so crucial as the PR valve above, if you keep careful watch over your fluid level.
Plumb it accordingly and adjust your bias as needed.
Keeping in mind that A-body disc brake systems have had chronic problems with premature rear lockup, your advice to get the adjustable valve is quite excellent. For all of the bodies, the lower control arms are sometimes different part numbers, though the interchange is correct. In most cases this is because of the swaybar option. A swaybar lower will obviously work on a non-swaybar car. The reverse would work, but would require the mounts to be fabricated or welded on
 
If you go with the B body brakes, you'll have to do something with the proportioning valve anyway, because you in theory are throwing the balance off.

That being said.

I have swapped out cars(not just A bodies) to front disc, and rear disc w/o the proportioning valve being changed, but I don't just stab my brakes when I stop either.

I would imagine if you can't find the disc swap, you'll have a harder time finding the drum swap, as there weren't as many made/left.

For the drums, you'll still need a big upper ball joint control arm, then any E or B body spindle, and drum set up. I also don't know how that spindle will affect your steering geometry.

Same money, poorer results.
 
Well then i say the heck with it, i've done this swap in the past, but its been about 10 yrs., i'll just stay with my little drum brakes & SBP wheels, i guess its going to get the Rallye wheels, my main purpose was to install the Summit Pro star wheels, i don't plan on running big MPH with this car, so unless i stumble on something cheap, it'll stay drums.
 
I read somewere,(cant find it now) that if you have an a body with 10 inch drums,you can reuse your original a body spindles to convert to b body 10 inch drums.Of course everything else has to come from the b body spindle,backing plate,brake hardware,and drums if course.I havent tried for myself,but i have a 71 b body with 10 inch front drums i was gonna try for heck of it.
 
This is the way i did it, i removed my original front drum setup and shelved them. I went to the wreckers and bought a pair of 10 inch drums and hubs off a wrecked A body. I then separated the hubs from the drums,took the hubs to the machine shop and had them redrilled for the 4 1/2 inch bolt pattern with screw in studs,bought new drums and had them drilled also. I did this back in the '80s,still on the car today,no problems.
 
JoeDust451 said:
I'm in Mo. now, its on a 71 Swinger i'm building, so what years of the FMJ & later B bodies do i need to look for?
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Were in MO are you? I might be able to hook you up with a junkyard on the eastern side that has a few F,M,J bodies in it.
 
and they are 5x4 1/2 bolt pattern.They work on the factory abody spindle.Also,the kelsey hayes disks from the amc hornets and gremlins will swap early small bolt disk cars to bigbolt with a rotor change.
 
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